The present invention relates to a mobile communication device having concealed antennas, and more particularly, to a mobile communication device having asymmetrical antennas that operate in multiple frequency bands.
Mobile communication devices typically include an antenna for transmitting and/or receiving wireless communication signals. It is desirable to design an antenna that allows wireless communication devices to operate in different frequency bands.
For example, GSM (Global System for Mobile communication) is a digital mobile telephone system that typically operates at a low frequency band, such as between 880 MHz and 960 MHz. DCS (Digital Communication System) is a digital mobile telephone system that typically operates at high frequency bands between 1710 MHz and 1880 MHz. PCS (Personal Communication Services), another digital mobile telephone system, uses a band between about 1850 MHz and 1990 MHz, and GPS (Global Positioning System) uses 1570 MHz band. It would be desirable to have the same mobile communication device working properly under these different frequencies. In order to achieve this goal, an antenna capable of transmitting and receiving signals in these frequencies has to be provided.
Certain design criteria must be followed in designing antennas for mobile communication devices. One such limitation is that the distance between the antenna and the circuit board should be larger than one-eighth the wavelength used by the communication device to avoid interference occurring therebetween. However, as the dimensions of mobile communication devices continue to reduce, this physical limitation is difficult to satisfy, especially for concealed antennas disposed inside the mobile communication devices.
Users of mobile communication devices, especially users of mobile phones, have been worried about possible health impacts caused by exposure to electromagnetic waves transmitted from and received by the antennas. One specific concern is that high frequency signals may cause brain tumors. Although there is insufficient medical evidence for such allegation, mobile phone users prefer antennas to be placed as far away as possible from their heads.
Therefore, there is a need for an antenna capable of transmitting signals in multiple signal bands. There is another need to reduce dimensions of wireless communication devices and at the same time suppress signal interference caused by the circuit board of the communication device. Still another need exists for placing mobile phone antennas as far away as possible from users. These and other needs are addressed by the present invention.
The invention provides a wireless communication device having a multiple frequency band antenna so that the wireless communication device is capable of working under different signal frequencies. The invention is advantageous in that the antenna is disposed in a location away from a user""s head, such as on the flip or slide panel of a mobile phone. The invention is also advantageous in providing an optimized design for concealed antennas and maintaining proper distance between the antenna and the circuit board of the wireless communication device.
A mobile communication device according to the invention comprises an antenna and a housing enclosing a circuit board having communication components disposed thereon to transmit and receive communication signals. The antenna includes a substrate having opposite first and second surfaces, a planar conducting layer, a quarter wave choke strip, and a monopole conducting layer. The planar conducting layer is disposed on the first surface of the substrate, while the quarter wave choke strip and the monopole conducting layer are disposed on the second surface of the substrate. The quarter wave choke strip is electrically coupled to the planar conducting layer and connected to the monopole conducting layer.
In one aspect of the invention, the antenna is configured to work in three frequency bands: an upper frequency ban, a middle frequency band, and a low frequency band. For example, the low frequency band may be the GSM band, the middle band may be the DCS band, and the upper band may be the PCS band. During operation, the monopole conducting layer may be configured to work as a monopole radiating in the upper frequency band, the quarter wave choke strip may be configured to work as the middle frequency band, and the monopole conducting layer, the quarter wave choke strip, and the planar conducting layer combined may be configured to work as the monopole radiating in the lower frequency band.
The antenna may be configured to operate in other numbers of bands, such as two bands, four bands, and so one. In addition, different operation frequencies may be selected depending on design requirements.
In anther aspect, the planar conducting layer has a substantially quadrilateral shape. The planar conducting layer may be coupled to the quarter wave choke strip via a metalized hole. The quarter wave choke strip may be substantially overlapping with the planar conducting layer.
The mobile communication device may have a panel slidely or rotatably attached to the housing. The panel may include a microphone for capturing a voice signal from the user. In one aspect, the substrate may be disposed on the panel. When the user slides or flips out the panel, the extended panel provides an extending portion from the housing. Thereby, the distance between the circuit board and the antenna is extended to avoid interference caused by the circuit board.
A multiple frequency band antenna according to the invention may include a substrate, such as a dielectric substrate, comprising opposite first and second surfaces, a first planar conducting layer, a conducting layer strip, and a second planar conducting layer. The first planar conducting layer is disposed on the first surface of the substrate and may have a substantially quadrilateral shape. The conducting layer strip is disposed on the second surface and has a free end formed within an area overlapping with the planar conducting layer, and a second end extending from the free end in an direction towards an edge of substrate. The conducting layer strip is coupled to the first planar conducting layer via a conducting device, such as a metal vial (metal hole).
In one aspect, the second planar conducting layer is configured to couple to a circuit board. As an alternative, the first planar conducting layer is configured to couple to a circuit board. The antenna may include a connecting device having a first end connected to the first planar conducting layer and a second end configured to couple to the circuit board.
In still another aspect, the antenna is configured to radiate in an upper frequency band, a middle frequency band, and a low frequency band. The second planar conducting layer may radiate as a monopole in the upper frequency band, the conducting strip may radiate in the middle frequency band, and the second planar conducting layer, the conducting strip, and the first planar conducting layer combined may radiate as a monopole in the low frequency band.
The conducting layer strip may be configured to work as an inductor in the low frequency band, and the second planar conducting layer does not overlap with the first planar conducting layer.
Still other advantages of the present invention will become readily apparent from the following detailed description, simply by way of illustration of the invention and not limitation. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the drawing and description are to be regarded as illustrative in nature, and not as restrictive.